The present invention relates to an improved apparatus which provides a connection between a completion riser and a drilling riser tension ring.
Risers, both drilling and completion risers, used on subsea wells normally do not have the strength to prevent buckling and normally such risers are maintained in tension which is supplied by the tension lines from the drilling rig or platform. Attaching the rig tension lines can be a laborious task for the rig hands who are suspended by air tugger lines underneath the rotary table. The rig hand must pull the drooping tension cables to the riser tension joint and shackle the cable ends to pad eyes on the joint. Because of the cable size and numbers (sometimes up to ten) connecting the tension lines to the riser tension joint can take a significant amount of rig time to perform.
Advancements have been made in connecting tension lines to drilling riser systems. A tension ring assembly with tension lines already connected is stored underneath the rotary table. Drilling riser joints are run through the tension ring in the conventional manner. The tension joint in the system is equipped with a large shoulder that mates with the tension ring. When this tension joint is lowered through the rotary, the tension ring is remotely locked onto the tension joint's shoulder and released from the rotary table. The riser string is then lowered with the tension lines already attached.
Completion riser technology has not kept pace with drilling riser technology. This is primarily due to the fact that drilling risers are predominantly owned by drilling contractors for specific rings. Improvements in handling and running drilling risers are customized to each ring. Completion risers on the other hand are predominantly owned by oil companies who may use the completion riser system on several different rigs. Because of this, completion riser systems are usually not designed for a specific rig.
Tension joints in completion riser systems have historically been a specialty joint containing four pad eyes. Run in the conventional manner, rig hands suspended on air tugger lines shackled the rig's tension lines onto the tension joint's pad eyes. Like the earlier drilling riser tensioning systems, this method of attaching the tension lines was a laborious task. If the rig was equipped with a drilling riser tension ring, the rig hands had to first disconnect the tension lines from the ring; thus, more labor was required to connect the tension lines to the completion riser. Recently a completion riser joint has been developed by a North Sea operator which was designed to mate directly with a particular rig's drilling riser tension ring. The tension joint included a standard completion riser joint with a circular ring of approximately 46.5 inches in diameter. When used in the field, the completion riser spider and the rotary table master bushings had to be removed in order to allow passage of the tension joint. Once passed, the master bushings and spider were repositioned back onto the rotary table. This proved to be a time consuming process. An object of the present invention is to provide an adapter apparatus for quickly and easily connecting a completion riser to a drilling riser tension ring which is supported under the platform, rotary table.
Another object is to provide an improved adapter apparatus which can connect to a completion riser and to a drilling riser tension ring to raise such tension ring by lifting on the completion riser tension ring and to tension the completion riser by exerting a tension on the drilling riser tension ring.
A further object is to provide an improved apparatus for connecting between a completion riser and a drilling riser tension ring which minimizes the difficult manipulations required of personnel suspended below the rotary table.
A still further object is to provide an improved apparatus for connecting between a completion riser and a drilling riser tension ring including a tension sleeve and an adapter tension ring with the tension sleeve having a size allowing it to be run through the rotary table without removing the spider and master bushings.